Friday, April 12, 2013

Dramatic changes in the ocean's environment could be one of the
reasons why the Moche, an early pre-Columbian civilization in Peru, fell
apart over 1000 years ago.

Moche pottery. Link to original: http://bit.ly/13UWSKB

Image credit: Juan Carlos Martins, http://bit.ly/11sxp7s

Upwelling of cold, deep water diminished because of changes in El
Niño in the Pacific, and interrelated climate changes upset the life of
the Moche (pronounced Mo-CHAY) in ways that undermined their social
structure and life so badly that within a few generations, their society
collapsed.

The history of that social catastrophe is told in clamshells, which reveal the local climate much like tree rings can.

The Moche Empire didn't suddenly collapse, said Fred Andrus, a geologist at the University of Alabama, in Tuscaloosa.

"The people adapted but did it in a way that was uncomfortable," he
said. "They faced a series of challenges and dealt with them in ways
that must have been difficult, and unpleasant."

The stable societies they built could not cope with the
difficulties. Civil wars may have broken out, along with civil unrest.
After a couple of centuries of upheaval new social organizations
replaced the old, and the Moche simply became a different people, a
culture known as the Chimu.

The Moche lived along the northern coast of Peru between 100 and
800 A.D., with a capital at Huacas del Sol y de la Luna near the
present-day towns of Moche and Trujillo. They were not an empire like
the Incas or Aztecs.

"The Moche were not a unified group," said Ryan Williams, curator
of South American Anthropology at the Field Museum in Chicago. "They
were several small kingdoms." Each of those kingdoms had a different
"trajectory," he said, so the collapse was not uniform.

"Most people now believe it was most likely a single religion
adopted by different people but with political power still local," said
Jeff Quilter, of the Peabody Museum of Archeology and Ethnology at
Harvard, in Cambridge, Mass., who was involved in the clamshell
research.

The Moche believed in gory human sacrifice and produced famously
beautiful pottery, built huge, bizarre brick pyramids and had a complex
and efficient irrigation system. Some of the aqueducts are still in use
today.

Their society was sophisticated and agriculture-based. Ruins of their cities remain tourist destinations in Peru.

But they disappeared by 800, and many scientists think changes in
the environment were largely responsible. Ice cores of glaciers in the
area hint at the same cause.

El Niño has been a suspect since the 1970s, with dramatic shifts in
the ocean pattern in the late 500s, Quilter said. The Moche seemed to
have recovered for a while before being "transformed" into another
people, he said.

Clamshells can provide more proof of these substantial climate
changes. Researchers from Alabama, and the Universities of Arizona and
Maine reported in the journal Geology
that the Moche buried clamshells with their dead as tributes. Because
of the climate and burial practices, Moche mummies are not uncommon.

According to Andrus, that combination makes it possible to produce a
snapshot of the environment at the time of burial. The science of
determining climate change through the study of shells is called
sclerochronology.

Clams draw carbon from the ocean as they grow, Andrus said. The
amount of carbon increases with upwelling. Cold ocean water is generally
richer in nutrients and animals than warmer water, and the colder the
water the more carbon there likely will be absorbed in the shells. These
can be found in growth bands and dated through radiocarbon
measurements.

By taking multiple samples of the shells, from the time a clam was
born until it died, it is possible to trace the upwellings, he said.

The clamshells support the theory that the pattern of El Niño
changed. El Niño is a wind-driven equatorial phenomenon in which warm,
nutrient-poor water replaces the cold, rich water off the South American
coast. The clams indicate the cycles of El Niño between the sixth and
the sixteenth centuries were more frequent and more intense than they
are now, Andrus said.

The climate changed with it. Fields flooded in some cycles, and
were replaced with sand dunes driven by extensive droughts in others,
evidence suggests. The floods may have destroyed some of the irrigation
canals, further altering the food supply, Andrus said.

Other factors likely played a role in the collapse of the Moche
society, Williams said, such as the eventual movement of highland
groups, including the Wari and the Cajamarca, into the Moche's
territory.

The effects on society would not have been sudden or dramatic, but
nevertheless, the Moche apparently had difficulties contending with the
changes, Andrus said. Eventually, they disappeared as a people.

"I think we can say climate change posed a severe challenge,"
Willams said. "It has as much to do with the social and political
configuration of their society as it does with the actual climate
impacts."

Joel Shurkin is a freelance writer based in Baltimore. He is
the author of nine books on science and the history of science, and has
taught science journalism at Stanford University, UC Santa Cruz and the
University of Alaska Fairbanks.

1 comment:

Joel, this article is heresy. There is a difference between a change in climate, and the almighty Climate Change. See, changes in climate are natural, normal variations. Climate Change is caused by mankind, the cancer of mother Gaia. Please, never use the trademarked phrase, Climate Change, unless you are blaming mankind's burning of fossil fuels.